Flow Sensor with Etched Glass Flow Path
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Solution Overview
Problem
Existing flow sensors for low gas flow rate measurement in semiconductor manufacturing face challenges in fabrication accuracy, sensitivity, and production efficiency due to issues with sandblasting methods, which result in inconsistent cross-sectional areas, poor transparency, and increased manufacturing costs.
Innovation Solution
A flow sensor design that bonds a sensor chip with a flow path forming member, where the flow path is formed by a transparent plate with inflow and outflow ports and a through hole, ensuring a fixed cross-sectional area and using materials with matching thermal expansion coefficients to prevent distortion, combined with a manufacturing method that uses dicing with masking to prevent swarf and coolant entry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If sandblasting is used to form the flow path in the glass chip, then the flow path can be created, but the cross-sectional area becomes inconsistent and transparency deteriorates
Solution Approach 1:
The patent replaces the mechanical sandblasting process with a photoresist-based patterning and etching process. A photoresist film is applied to the glass chip, exposed through a mask to define the flow path pattern, developed to create openings, and then etched to form the flow path with precise cross-sectional dimensions. This substitution of mechanical sandblasting with a photolithographic process ensures consistent cross-sectional area while maintaining transparency.
2Measurement precision
If the flow rate detecting part is made thin and small to increase sensitivity, then measurement precision improves, but the part becomes vulnerable to damage from swarf and coolant during dicing
Solution Approach 1:
The patent applies a protective mask or cover to the flow rate detecting part before the dicing process. This preliminary protective action prevents swarf and coolant from entering the flow path and damaging the sensitive detecting part during wafer separation. The protection is removed after dicing, allowing the sensitive thin and small detecting part to maintain its high measurement precision without compromise to reliability.
3Adaptability or versatility
If individual sensor chips are separated before bonding with glass chips, then assembly flexibility increases, but production efficiency decreases
Solution Approach 1:
The patent combines multiple sensor chips and glass chips into a single integrated assembly unit. Instead of separating and individually assembling components, the invention bonds multiple sensor chips to corresponding glass chips in a coordinated manner, creating a modular assembly that can be produced efficiently while maintaining assembly flexibility for different configurations.
4Stability of the object's composition
If the cross-sectional area of the flow path is increased to reduce individual differences, then flow rate measurement stability improves, but manufacturing complexity increases
Solution Approach 1:
The patent optimizes the cross-sectional area parameters of the flow path by precisely controlling the photoresist thickness, exposure conditions, and etching parameters. This parameter optimization achieves the desired cross-sectional dimensions that reduce individual differences between sensors while maintaining a relatively simple flow path structure without unnecessary complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design stabilizes flow rate detection accuracy, improves transparency, reduces production costs, and enhances the durability and sensitivity of the flow sensor while maintaining measurement precision.
Implementation Method 1
The sensor chip has a heater (Rh) that is formed with an electric insulating film layer on the upper surface of a silicon substrate
Implementation Method 2
The platinum thin film functions as a temperature measurement resistor because the resistance value thereof changes according to temperature
Implementation Method 3
The central part on the upper surface of the silicon substrate formed with the heater (Rh), the upstream-side temperature measurement sensor (Ru), and the downstream-side temperature measurement sensor (Rd) is formed into a concave part by removing the silicon in the lower part thereof by anisotropic etching
Data Source
AI summary
A flow sensor may be formed by bonding a sensor chip formed with a flow rate detecting part and a flow path-forming member that is provided on the sensor chip and is formed with a flow path for a fluid flowing in the flow rate detecting part to each other on the upper surface of a substrate. The flow path-forming member may be formed by bonding a transparent first flow path forming member and a second flow path-forming member to each other. The first flow path forming member has a plate shape, and is provided with an inflow port and a outflow port for the fluid to be measured, and the second flow path forming member has a plate shape, and is provided with a through hole that forms the flow path along the flow of the fluid flowing along the flow rate detecting part.